1. Technical Field
The present invention relates to systems and methods for reducing the reverberation in a captured audio signal, in particular by estimating a reverberation time of the capture environment.
2. Description of the Related Art
A number of techniques have been proposed in the past for de-reverberation. These methods include multi-channel approaches and single channel approaches. A common single channel de-reverberation approach is spectral subtraction. Prior publications on spectral subtraction include “About this dereverberation business: A method for extracting reverberation from audio signals,” Proceedings of 129th Convention, Nov. 4-7, 2010, by G. A. Soulodre; “Subband dereverberation algorithm for noisy environments,” IEEE International Conference on Emerging Signal Processing Applications, January 2012, by Guangji Shi and Changxue Ma; “Joint dereverberation and residual echo suppression of speech signals in noisy environments,” IEEE Transactions on Audio, Speech, and Language Processing, Vol. 16, Issue 8, pp. 1433-1451, November 2008, by E. A. P. Habets, S. Gannot, I. Cohen, and P. C. W. Sommen; “A decoupled filtered-X LMS algorithm for listening room compensation,” Proceedings of IWAENC, 2008, by Stefan Goetze, Markus Kallinger, Alfred Mertins, and Karl-Dirk Kammeyer; and “Analysis and Synthesis of Room Reverberation Based on a Statistical Time-Frequency Model,” 103rd Conv. Audio Engineering Society, September 1997, by Jean-Marc Jot, Laurent Cerveau, and Olivier Warusfel.
In these types of approaches, an impulse response for a reverberant environment is modeled as a discrete random process with exponential decay. These approaches may be extended by estimating the magnitude of the impulse response using a minimum ratio of the magnitude of a current frequency block to that of a previous frequency block. The reverberant signal may then be removed using spectral subtraction-based algorithms such as in the publications by Shi and Habets.
In de-reverberation, it is important to have a good estimate of the reverberation time. This helps to ensure that spectral subtraction-based de-reverberation works well with reverberant audio signals. Inaccurate estimation of reverberation time may lead to over-subtraction of late reverberation and generate annoying artifacts such as music noise.